As design rules have been increasingly reduced with miniaturization, variation in line width due to an optical proximity effect has become ignorable. The optical proximity effect is a phenomenon in which a finished value of a line width varies according to a distance to a proximate line. The optical proximity effect degrades the dimensional precision of wiring. Accordingly, depending on a line-to-line space, the line width is reduced to a value smaller than a specified value under the influence of the optical proximity effect and, in some cases, may result in wire breakage.
Therefore, it is essential to compensate for the influence of the optical proximity effect by OPC (Optical Proximity effect Correction). The OPC is a technique which predicts an amount of variation in line width resulting from the line-to-line space, performs correction so as to offset the amount of variation, and holds a finished line width constant.
For example, as a method for preventing variation in the line width of polysilicon wiring, the technology disclosed in Patent Literature 1.    Patent Literature 1: Japanese Laid-Open Patent Publication No. H 10-32253 has been known.